Proliferative vitreoretinopathy (PVR) is a mutifactorial disease in which the growth and contraction of an epiretinal membrane (ERM) leads to retinal detachment. The cells within the ERM express both growth factors and receptors for these growth factors. The immediate goal of this proposal is to test the hypothesis that growth factors drive the formation of an ERM and hence PVR. 1. Construct and characterize a series of dominant negative growth factor receptors. A. Construct dominant negative growth factor receptors. We will focus on the PDGF, VEGF and HGF receptors, which have been strongly implicated in PVR. Dominant negative reagents will be constructed and screened for efficacy in tissue culture cell lines. B. Characterize the ability of the dominant negative receptors to prevent PVR. The dominant negative reagents will be tested for their ability to block PVR in a rabbit model of the disease. 2. Identify signal relay enzymes that are involved with PVR. Cells expressing the PDGF alpha receptor (aPDGFR) are able to efficiently induce PVR, whereas cells that do not express this receptor have a very low PVR potential. We will compare the PVR potential of a panel of cell lines expressing aPDGFR mutants that selectively fail to engage signal relay enzymes. 3. Monitor the activation state of relevant signaling enzymes during disease progression. Specific aims 1 and 2 will identify receptors and signaling enzymes that are required for PVR in an animal model. Activation of such proteins involves phosphorylation, and thus phospho-specific antibodies can be used to monitor their activation state within the ERM. We will develop phosphospecific antibodies to each of the targets identified, and use them to determine at what times these proteins are activated during the course of the disease in the animal model. In addition, we will use phosphospecific antibodies to test if the signaling enzymes are active in human ERMs. These studies will identify molecules that make a critical contribution to PVR, and hence significantly advance our understanding of the disease. An additional outcome of this proposal will be the development of reagents to manage and/or prevent PVR. Hence the fruits of this proposal will form the basis for future efforts aimed at our long-term goal of developing a safe and efficient gene therapy-based approach to prevent PVR.